Conventionally, a fuel reformer which generates hydrogen from fuel and water vapor is known (see, for example, JP-A-2003-119002). A conventional technology described in JP-A-2003-119002 includes a structure by stacking in a multi-layer manner, for example, a fuel reforming catalyst layer which produces hydrogen through steam reforming of fuel, and a hydrogen permeable film through which hydrogen permeates selectively from gas having the hydrogen generated by the steam reforming as a main component.
According to this conventional technology, methanol (Me—OH) is used for the reformed fuel, and the hydrogen permeable film made of palladium alloy is disposed so as to face a gas passage through which the gas including hydrogen as a main component flows. A reaction formula for a reaction produced in the gas passage is expressed in the following chemical formula 1.MeOH→H2+CO  Chemical formula 1
When hydrogen is separated through a hydrogen separating film, the above-expressed reaction is put into a state of non-equilibrium. Accordingly, the amount of hydrogen generated can be increased. Therefore, temperature of the above reaction can be reduced, and a reforming temperature can be lowered.
However, according to the above conventional technology described in JP-A-2003-119002, the hydrogen permeable film is used for a means for separating hydrogen from the gas (reformed gas) generated by reforming. Thus, given a strength of the film, a flow rate of the hydrogen separated from the reformed gas cannot be increased, and moreover, a pressure difference (differential pressure) between upstream and downstream sides of the film is difficult to secure. For this reason, in order to secure by their desired amount the flow rate of the hydrogen separated from the reformed gas and the differential pressure between the upstream and downstream sides of the film, it is necessary to increase an area of the hydrogen permeable film, and a size of the entire fuel reformer thereby increases.
In addition, according to the conventional technology of JP-A-2003-119002, since the hydrogen permeable film is fixed in a frame body, there needs to be the seal between the hydrogen permeable film and the frame body. The fuel reformer of the above conventional technology has a structure obtained by stacking the hydrogen permeable film, the fuel reforming catalyst layer and so forth in a multi-layer manner. As a result, a seal length becomes long. Thus, a lot of labor needs to be put into the sealing, and a production cost also becomes high. Furthermore, the palladium alloy which is an expensive precious metal is used for a material of the hydrogen permeable film. Therefore, the production cost becomes even higher.